1. Field of the Invention
The present invention relates to a process for the preparation of an electrode. It typically but not exclusively applies to the fields of the electrodes for the production of hydrogen by the electrochemical route.
2. Description of Related Art
Many research studies are currently being carried out with the aim of finding products which can be substituted for the noble metals used as electrode in the production of hydrogen. However, the existing methods are very expensive since they use precious metals for the electrode materials, in particular platinum, which is one of the best catalysts for the electrochemical production of hydrogen.
FR 2 573 779 describes a process for the preparation of an activated electrode for the production of hydrogen, said electrode being obtained by bringing an electrode composed of a glassy carbon into contact in an acidic medium with a dilute aqueous solution of a polyoxometalate, such as, for example, SiW12O40H4, and by then bringing said electrode to a cathode potential sufficient to produce a reduced form of the polyoxometalate. This process employs a relatively inexpensive material but is carried out with a negative potential which requires a large amount of electrical energy. Furthermore, this process requires exclusive use of highly acidic media (pH in the vicinity of 0) and it is not possible to optimize the thickness of the catalyst film obtained by this method, the efficiency of the catalyst depending on said thickness.
Furthermore, patent applications US 2006/0141334 describes a catalytic electrode for the adsorption of carbon monoxide CO or the oxidation of methanol. The electrode comprises in particular a partial salt of a solid heteropolyacid doped with a noble metal, such as, for example, with Pt or Ru, or with a transition metal and having a molecular weight ranging from 800 to 10000. This polyacid can be applied to the surface of a carbon electrode, in the form of a mixture with an organic or inorganic binder. In example 1, a powder composed of a mixture of a heteropolyacid of formula Na5H3[PtW6O24]. xH2O comilled with acetylene black is dispersed in a 5% solution of Nafion in a solvent, the nature of which is not specified. The mixture is subsequently applied to a glassy carbon electrode and then dried at ambient temperature. The electrode thus obtained can subsequently be used for the oxidation of methanol. However, such an electrode is not active with regard to the reduction of protons to give dihydrogen. This is because, when this electrode is tested in cyclic voltammetry (used to test the activity of all the electrodes with regard to their ability to reduce protons), only the waves characteristic of polyoxometalates are observed (see, for example, Bineta Keita and Louis Nadjo, Materials Chemistry and Physics, 1989, 22, 77-79). patent applications US 2006/0141334 furthermore does not envisage the use of electrodes of this type in the production of hydrogen by the electrochemical route.